The vas deferens is a sperm carrying duct tubes that begins at the
testicles and end at the urethra. During ejaculation sperm that are
stored in the epididymis move up along the duct tubes into the
ejaculatory duct and expelled from the body. The vas deferens tubes are
cut or block in the process called
male sterilization
which prevent sperm from being ejaculated and is the permanent method of birth control for men.

Seminal Vesicles

The seminal vesicles are small glands that produce alkaline fluid
which make up large portion of seminal fluid released during
ejaculation. The vas deferens move sperm from epididymis into
ejaculatory duct and combine with seminal fluid empty from seminal
vesicles into ejaculatory duct. The alkaline fluid protects sperm from
acidic environment and allowed sperm to survive longer in the vagina.

Prostate Gland

The prostate gland is located underneath the bladder and is made
up of muscle fibers and glandular tissues. The prostate gland is about
the size and shape of a walnut and produces about 80% of the seminal
fluid released during ejaculation. The prostate gland control the flow
of urine by closing the urinary opening to the bladder preventing urine
from passing through during ejaculation and only passes semen out from
the body.

Cowper’s Glands

The cowper’s glands are about the size of a pea located
underneath the prostate gland. The cowper’s glands are located one on
each side of the urethra that secrete small amount of fluid during
sexual arousal. The fluid usually appears as droplets at the tip of the
penis and varies among men. Some men produce droplets after sexual
arousal, some produce droplets immediately after achieving erection, and
some never produce droplets after achieving arousal or erection.

Semen

Semen contains sperm and seminal fluid produced by seminal
vesicles, prostate gland, and cowper’s glands. In a single ejaculation
semen contain between 200 and 500 million sperm. Semen is made up of
citric acids, water, enzymes, fructose, proteins, potassium,
prostaglandins, and variety of other substances. Semen is not harmful
when swallow during oral sex, but HIV infected semen can transmit the
virus through open sores or bleeding gums in the mouth.

Ejaculatory Duct

The ejaculatory duct passes through prostate gland and opens into the urethra that passes semen out of a man’s body.

Urethral Opening

The urethra is the tube connecting the bladder and ejaculatory
duct to the urinary opening that passes urine and semen out of a man’s
body.